I'll start by saying that I don't know any off the top of my head that have Peter and Jean Grey as a pairing. HOWEVER! If it's crossovers you're looking for, I have a trio of recommendations for you.
1:
Everybody Loves Spidey, by Maximus Reborn. It's a series of one shots (some of which became two shots) which deal with Spider-man and his relationships with a bunch of different women. I don't recall it being a particularly 'deep' or thought provoking piece, and it hasn't updated in something like a year; all the same, it's well edited and a decent read.
2:
Caught in the Web, by Frivolous Thoughts. Started this in direct response to the Maximus Reborn fic I listed above. Also good, also hasn't been edited in a while. My big criticism of this one is that the author uses polls to determine what to write, and uses a lot of crossovers that (to me) don't seem to make a lot of internal sense, particularly the ones with the video game characters.
3:
Spider-Man hearts Jenny W., by Snorpenbass: Easily the most well-written of the three. Peter, helped along by a tremendous amount of alcohol, ends up sleeping with an equally annihilated Jennifer Walters. From these humble seeds a genuine relationship develops. It features cameos from the Fantastic Four, which are excellent. It also hasn't been updated in years, which makes me sadder than I can say.
Enjoy!
